The present disclosure relates generally to switching mode power supplies, and more particularly to switching mode power supplies with constant ON-time control.
Almost all electronic appliances require power supplies. A power supply converts for example an alternating-current (AC) voltage of a power grid into a power source with specific ratings demanded by the core circuit of an electronic appliance. Among all kind of power supplies, switching mode power supplies are known to be compact in size and efficient in power conversion, and therefore they are broadly adopted by power supply manufactures. Switching mode power supplies normally use pulse width modulation (PWM) technology to control power conversion.
In order to reduce the burden of building a huge power grid system and stabilize the output of a power grid, loads to the power grid are usually required by regulations to have high power factors, and power supplies are no exception. Methods for increasing the power factor of a switching mode power supply include, among others, one-cycle control and constant ON-time control, each having its own benefit over the others. Constant ON-time control is suitable for operating in discontinuous current mode (DCM), and the circuit to implement constant ON-time control is considerably simple. Therefore, constant ON-time control is welcome in the applications of low-power or middle-power switching mode power supplies.